V. A. Lagoda, I. O. Parasyuk, and A. M. Samoilenko, “Lipschitzian invariant tori of indefinite monotone system”, Ukr. Mat. Zhurn., vol. 64, no. 3, pp. 363–383, Mar. 2012, Accessed: Apr. 09, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/2582